1. Field of the Invention
The invention refers to a progressive distributor with three or more control pistons each of which can be displaced in a housing bore of a distributor housing, which progressive distributor each time with delivery of a specific quantity of lubricant through a frontal outlet, which outlet leads from one of two annular grooves of the housing bore of the respective preceding control piston, from which lubricant fed in under pressure through a housing inlet is alternately pressed into its two final positions in the respective housing bore. The control pistons, through the two annual grooves, are sequentially controlled by the lubricant in such a manner that the next control piston cannot be displaced by the lubricant until the piston displacement of the preceding control piston has been completed or nearly completed. The housing bores are connected with the inlet through a central bore, whereby in each case a channel connects an annular groove of the respective housing bore of the preceding control piston with the front face of the particular housing bore of the next control piston and specifically, except for one control piston, with annular groove and front face on the same side, but in the case of the one control piston with annular groove and front face on opposite sides.
2. Description of Related Art
Such a progressive distributor is known from DE 34 05 690 C2. To design such a progressive distributor with additional functions and thereby make it suitable for novel applications, especially also in those cases where machines must be lubricated with very small quantities or where some lubricating points must be attended to frequently, but others, e.g. only daily, weekly or monthly, it is proposed that in each case a connecting channel connects the respective front faces of at least one housing bore although not of all housing bores with a front face of an additional piston whereby an additional piston is mounted so that it can be moved to and fro between two stops by the lubricant, whereby at least one piston must act against an outlet pressure that is higher than the outlet pressure against which the additional piston acts and whereby for the production of the higher outlet pressure the corresponding outlets feature an overflow valve or a non-return valve with counterpressure. In an alternative solution the arrangement with the overflow valves or non-return valves with counterpressure, the additional piston can have at least one circumferential groove which only releases an outlet of a piston in the two final positions of the additional piston. With such progressive distributors, when the respective piston to whose housing bore the additional cylinder is connected is moved from one side to the other through load on one front face, the outlet assigned to this piston not only delivers the quantity of lubricant displaced by the opposite front face of this piston, but also through displacement of the additional piston from its final position at one end to the opposite end an additional quantity of lubricant corresponding to the free volume of the additional cylinder.
With the one solution the displacement cylinder of the individual pistons pauses long enough until the entire contents of the additional cylinder are emptied, because at least one of these other pistons had to displace itself against an outlet pressure higher than the outlet pressure that the additional piston must overcome allowing for friction losses. With the other solution the additional piston blocks the required outlet for the continuation of the displacement cycle of the pistons long enough until the additional piston has been displaced from its one final position to the other and its circumferential groove releases the required outlet for the continuation of the displacement cycle. The first solution variant has the advantage that the piston can be varied without interrupting the stroke. The second solution variant has the advantage that it works reliably under all pressure conditions, because it does not depend on increased counterpressure at least two opposite outlets of a piston. In both cases the progressive distributor works with the one additional cylinder as a hydraulic timing element, whereby the delay for the continuation of the displacement cycle is determinable or determined by the volume of the additional cylinder.